Addition of phenylnitrenium ion to olefins. Reactions of phenyl azide with some olefins in the presence of trifluoroacetic acid

Abstract

Addition to cyclohexene, cis- or trans-4-methylpent-2-ene, or hex-1-ene of a singlet phenylnitrenium ion, generated from phenyl azide in the presence of trifluoroacetic acid, gave stereo- or regio- specifically N-phenyl-β-hydroxyamines (after work-up with aqueous Na₂CO₃)via aziridinium ions together with N-allyl- and 2- and/or 4-allylanilines. Use of methyl acrylate or methyl crotonate as an electron-deficient olefin led to the formation of N-phenylserine or N-phenylthreonine methyl ester (after work-up with aqueous Na₂CO₃), respectively. In the reaction with 1,1-disubstituted ethylene or styrene derivatives, N-substituted anilines were formed through an attack of either tertiary alkyl or benzylic cations on phenyl azide.